Sept 10 (Reuters) - The U.S. Food and Drug Administration has proposed stronger safety language on labels of long-acting and extended-release opioids in response to an epidemic of overdoses and deaths from the widely used pain medicines.

The labels need to highlight dangers of abuse and possible death, as well as risks to newborns of mothers taking the medicines, the agency said on Tuesday.

Opioids include formulations of morphine, oxycodone and fentanyl. One of the best-known opioids is Oxycontin, a long-acting form of oxycodone.

Some 16,651 people in 2010 died from overdose deaths related to opioid abuse, the FDA said, including long-acting formulations.

In a conference call, FDA officials said long-acting forms of opioids have played a "disproportionate role" in drug abuse and deaths.

The FDA said the drug labels currently are indicated for patients with moderate to severe pain, but in the future will indicate they should only be used for severe pain.

"The FDA is invoking its authority to require safety labeling changes and postmarket studies to combat the misuse, abuse, addiction, overdose and death from these potent drugs that have harmed too many patients and devastated too many families and communities," FDA Commissioner Margaret Hamburg said in a release.

Updated language in the drug labels will stress the medicines are meant for pain severe enough to require daily, round the clock, long-term opioid treatment, and only for those who have not had adequate pain relief from alternative medicines.

The labels will also include prominent boxed warnings that chronic maternal use of the drugs can result in potentially fatal opioid withdrawal syndrome in newborns.

The agency will require extra studies of the drugs to assess known risks of abuse, overdose and death.

Janina Kean, chief executive of High Watch Recovery Center, an addiction treatment facility in Kent, Connecticut, said stronger safety language by itself won't make a noticeable dent in the numbers of addictions and overdoses of opioids.

She said the drugs are being prescribed for countless uses, many of which are far from severe, with no apparent oversight.

"Doctors are prescribing them for dental work, for chronic back pain and every ache and pain you can imagine," Kean said. "The FDA would be better served by trying to regulate when doctors prescribe those drugs."

Kean said about 20 to 25 percent of her substance-abuse clients are addicted to opioids, up from just 1 to 4 percent a decade ago.

"It's getting worse," she said, noting that many clients are teenagers or young adults who became addicted by going into their parents' medicine cabinets and taking their legally prescribed opioids.

"But now, when they go to the street they cant afford the opioids. So they go to heroin, which is also an opioid, because it's cheaper."

Morgan Liscinsky, an FDA spokesman, said the agency's hands are largely tied. While the FDA has authority to regulate drugmakers and drug labeling, he said it cannot intervene with doctors.

"The FDA does not have the authority to regulate the practice of medicine, and health care practitioners may choose to prescribe a legally marketed drug, based on their clinical assessment," Liscinsky said.